1. Field of the Invention
This invention relates to string stretching mechanisms for stringed instruments, in particular to tremolo mechanisms of electric guitars.
2. Description of the Related Art
Conventionally, electric guitars have tremolo mechanisms, that is, string stretching mechanisms, which produce special sound effects called ‘tremulous effects’ by rapid reiteration of notes or by rapid alternation between notes, wherein tensions of strings are repetitively varied at relatively high frequencies (or in small periods) to slightly shift up and down pitches. This technique may be disclosed in various papers such as Japanese Unexamined Utility-Model Publication No. Hei 2-119300.
FIG. 6 shows a conventional example of a tremolo mechanism of an electric guitar, that is, a tremolo mechanism 1 that is arranged on a prescribed position of a body 2 of the guitar, wherein a bridge base 3 arranged on the body 2 is interconnected with a balance spring 4, which is embedded in the body 2. The bridge base 3 is balanced with the moment caused by tension T1 of a string 5, which is stretched above the body 2, by the balance spring 4. One end portion of the string 5 is supported by a bridge saddle 6 arranged on the bridge base 3, the front end portion of which is securely fixed to the body 2 by a support screw 8, wherein a contact point or area between the support screw 8 and the front end portion of the bridge base 3 acts as a fulcrum for a rotational movement of the bridge base 3, the back end portion of which is interlocked with a tremolo arm 7. By vertically moving the tremolo arm 7 in FIG. 6 up or down, the bridge base 3 is correspondingly moved up or down to temporarily break the balanced state established against the moment, so that the tension T1 of the string 5 is repetitively varied at a relatively high frequency. The string 5 has a ring 9 at one end thereof, which may be normally called a “ball end” that is stopped beneath the lower portion of the bridge base 3. The intermediate portion of the string 5 is stretched and supported between the bridge saddle 6 and a nut of a neck (not shown), and the other end of the string 5 is stopped and wound about a winder of a tuning peg arranged in a head (not shown).
The bridge saddle 6 can be arbitrarily adjusted in height above the bridge base 3 by two height adjustment screws 10. In addition, the bridge saddle 6 is also arranged to be freely moved forward and backward above the bridge base 3. That is, the bridge saddle 6 is interconnected with the back end portion of the bridge base 3 to be freely moved forward and backward by an octave adjustment screw 11, which is used to adjust intonation of the string 5, wherein the bridge saddle 6 is normally pulled backwardly by a spring 12. Generally, it can be said that accurate intonation is established when accurate pitches can be normally produced by fingering the string 5 at all frets of the neck of a guitar. Musicians may judge the intonation based on lengths of strings, overall curves of necks, used states or oldness of strings, and the like. A projecting portion 3A is integrally formed at the back end portion of the bridge base 3 and is interconnected with the octave adjustment screw 11. In addition, a string stopper 3B projects downwardly from the lower portion of the bridge base 3, so that one end portion of the string 5 is inserted through the string stopper 3B, which is arranged in a spring receiving hollow 13 of the body 2 of the guitar and is also used to stop one end of the balance spring 4.
The conventional tremolo mechanism 1 described above requires a relatively large number of parts and has a complicated structure, which raises a problem that a relatively long time may be required for manufacture and adjustment. Normally, the neck of the guitar is slightly curved in a convex shape in the direction perpendicular to the longitudinal direction in which six strings are arranged and stretched, so that the fingerboard of the neck is correspondingly curved. That is, all strings may slightly differ from each other in heights above the fingerboard of the neck of the guitar, wherein the strings arranged approximately in the center area in the width direction of the neck have higher heights while the other strings arranged in peripheral areas in the width direction of the neck have lower heights. On the other hand, an upper surface 3a of the bridge base 3 is normally formed planar. Therefore, it is necessary to perform fine adjustment on strings in response to their heights. This requires two height adjustment screws 10 for use in adjustment of the height of the bridge saddle 6, which is supported above the upper surface 3a of the bridge base 3. For this reason, the number of parts should be correspondingly increased; and a relatively long time should be required for adjustment of the height of the bridge saddle 6 above the bridge base 3.
Since the height adjustment screw 10 vertically penetrates through the prescribed position of the bridge saddle 6, there is a possibility that the upper end of the height adjustment screw 10 will be projected upwardly to be considerably higher than the upper surface of the bridge saddle 6 in adjustment, which may cause problems in that player's hand would be easily brought into contact with the height adjustment screw 10 during the playing of the guitar. In addition, unwanted vibration and noise may be caused due to the increased number of parts particularly arranged in the tremolo mechanism 1. In order to interconnect the back end portion of the bridge saddle 6 with the bridge base 3 by the octave adjustment screw 11, it is necessary to form the projecting portion 3A integrally at the back end portion of the bridge base 3. That is, the projecting portion 3A as well as the octave adjustment screw 11 and the height adjustment screw 10 should be apparently arranged on the body 2 of the guitar, which may deteriorate visual appearance of the tremolo mechanism 1.